jimboaw
New member
Ok, just replaced all the standing rigging. What is the minimum rig tension % I should use before taking her out for fine tuning ? Deck stepped. Masthead Rig. double spreaders 10 mm HS/BS. 8 mm shrouds.
At the dock rig tension.
- Thread starter jimboaw
- Start date
pvb
Well-known member
Optimum tension is generally considered to be about 15% of the wire’s breaking strain for the cap shrouds; less for the lowers; and about 20% of breaking strain for the backstay on a masthead sloop.
Salty John
Active member
Here is some info on rig tension: The following table gives recommended initial tension settings for 1 x 19 wire rope. It should be noted that optimal rig tension will be a function of the boat design, the rig and the cut of the sails. Headings are: wire diameter, wire breaking strength, forestay tension, shroud tension.
2.5mm 550 kg 80 kg 55 kg
3.0mm 950 kg 145 kg 110 kg
4.0mm 1500 kg 230 kg 160 kg
5.0mm 2000kg 340 kg 230 kg
5.5mm 2800 kg 450 kg 320 kg
6.0mm 3700 kg 590 kg 390 kg
7.0mm 4500 kg 680 kg 450 kg
Forestay tension – masthead rig: It is almost always advantageous to set the forestay tension as high as possible within the limits of structural strength. Generally, it is possible to use 15% of the breaking strain of the wire as the forestay tension. The backstay should be adjusted to maintain a straight mast with the desired forestay tension. The backstay tension will be less than the forestay tension because the backstay makes a greater angle to the mast than does the forestay.
Note that rollerfurling jib tension can only be set by adjusting backstay tension.
Forestay tension – fractional rig: Because the forestay tension cannot be directly balanced by the backstay tension some mast bend is accepted and the sails are cut to accommodate it. Forestay tension of at least 15% of the wire strength is desirable but, if this results in excessive mast bend, it may be necessary to back off the tension.
Upper and lower shroud tension – masthead rig: The initial rig tension should be high enough that the leeward shrouds do not go slack when sailing close-hauled in a brisk breeze. The proper tension for your boat can be found by a few test runs under sail and then a tension gauge can be used to record and maintain this value.
For many boats a shroud tension of 10% to 12% of the wire strength is adequate. In some rigs it may be advantageous to carry a bit more tension in the uppers than the lowers.
Upper and lower shroud tension – fractional rig: In most cases the same comments apply as for masthead rigs. However, there is one exception. Where the upper and lower shrouds on a fractional rig lead to chainplates located aft of the mast – swept back spreaders – most of the forestay tension is balanced by the upper shrouds. A shroud tension as high as 20% of the wire strength may be required to achieve the desired forestay tension. Never exceed 25% of the wire breaking strength.
This information is mainly from Loos & Co, makers of the Loos Tension Gauge. They are located near you in Naples, Florida.
2.5mm 550 kg 80 kg 55 kg
3.0mm 950 kg 145 kg 110 kg
4.0mm 1500 kg 230 kg 160 kg
5.0mm 2000kg 340 kg 230 kg
5.5mm 2800 kg 450 kg 320 kg
6.0mm 3700 kg 590 kg 390 kg
7.0mm 4500 kg 680 kg 450 kg
Forestay tension – masthead rig: It is almost always advantageous to set the forestay tension as high as possible within the limits of structural strength. Generally, it is possible to use 15% of the breaking strain of the wire as the forestay tension. The backstay should be adjusted to maintain a straight mast with the desired forestay tension. The backstay tension will be less than the forestay tension because the backstay makes a greater angle to the mast than does the forestay.
Note that rollerfurling jib tension can only be set by adjusting backstay tension.
Forestay tension – fractional rig: Because the forestay tension cannot be directly balanced by the backstay tension some mast bend is accepted and the sails are cut to accommodate it. Forestay tension of at least 15% of the wire strength is desirable but, if this results in excessive mast bend, it may be necessary to back off the tension.
Upper and lower shroud tension – masthead rig: The initial rig tension should be high enough that the leeward shrouds do not go slack when sailing close-hauled in a brisk breeze. The proper tension for your boat can be found by a few test runs under sail and then a tension gauge can be used to record and maintain this value.
For many boats a shroud tension of 10% to 12% of the wire strength is adequate. In some rigs it may be advantageous to carry a bit more tension in the uppers than the lowers.
Upper and lower shroud tension – fractional rig: In most cases the same comments apply as for masthead rigs. However, there is one exception. Where the upper and lower shrouds on a fractional rig lead to chainplates located aft of the mast – swept back spreaders – most of the forestay tension is balanced by the upper shrouds. A shroud tension as high as 20% of the wire strength may be required to achieve the desired forestay tension. Never exceed 25% of the wire breaking strength.
This information is mainly from Loos & Co, makers of the Loos Tension Gauge. They are located near you in Naples, Florida.
RichardPerou
New member
Great info. Now, how do I mesure the tension?
Salty John
Active member
You use a Loos Tension Gauge. There are actually three sizes covering wire diameters from 2.5mm up, but two cover most recreational boat wire sizes: The standard guages are the type A(91M) for 2.5mm to 4mm wire and the type B(90M) for 5mm to 7mm wire. There is a larger size for bigger wire. There is also a Pro range, slightly more accurate and a bit more expensive. Chandlers sell tham for £40 to £60. Search on eBay for a better deal.
jimboaw
New member
Thanks folks, the guy on my port side has the "Pro" tension guage so will play with it today.
jimboaw
New member
Ok. did my playing and set everthing around 15% . Stick up straight, new furler installed no major sag in luff sections. Guess what, 3 hours later all down to 12%.+/- This was as the temprature was falling. New rigging stretching? Using my neighbours Loos Pro, Good bit of kit. How long should I continue to monitor tension before sea trials?
john_morris_uk
Well-known member
If the rigging is new as you say, then I suspect that the decrease in tension is down to stretch. New 1 by 19 stretches at first - should settle down after a few weeks.
dodgie
New member
I have a fractional rig (folkboat) and noticed the other day that the lower shroud rigging wires are much looser than the upper shroud wires. And by loose I mean not under much tension. Clearly this is Not Good. Bottlescrew base does not turn easily (if at all) so I've hit with WD40 and will have a shot at tightening tomorrow - at least to a 'by-feel' level of tightness before attmepting to gauge it. Sound sensible/desirable??
A
angelsson
Guest
HI,
How does the gauge work in practice, does it fit 'in-line' and then have to be removed, or does it clamp on the cable recording its tension. Of great interest to me as I may be removing mast later this year to use French canals.
Thank you,
Mike
How does the gauge work in practice, does it fit 'in-line' and then have to be removed, or does it clamp on the cable recording its tension. Of great interest to me as I may be removing mast later this year to use French canals.
Thank you,
Mike
Strathglass
New member
The tension gauges clip on to the wire with the mast fully rigged.
You effectively distort the shroud to a mark on the gauge and read from a scale which will give you a rig tension reading.
Each gauge covers a range of wires. I have one for dinghies (3-4-5mm) and another one for up to 8mm.
I do not expect them to be ultimately accurate but they are repeatable and will give me reliable relative readings.
I think I bought the bigger one from Jimmy Green Marine.
www.jimmygreen.co.uk/Shop/products.asp?iCatID=52&iSubCatID=48
Iain
You effectively distort the shroud to a mark on the gauge and read from a scale which will give you a rig tension reading.
Each gauge covers a range of wires. I have one for dinghies (3-4-5mm) and another one for up to 8mm.
I do not expect them to be ultimately accurate but they are repeatable and will give me reliable relative readings.
I think I bought the bigger one from Jimmy Green Marine.
www.jimmygreen.co.uk/Shop/products.asp?iCatID=52&iSubCatID=48
Iain
A
angelsson
Guest
Hi Ian,
Thanks for your reply and info, I think I will need something (from memory) more than 4mm as the Jimmy Green one is.
Backstays something like 10mm. and shrouds possibly 6mm.
Regards
Mike
Thanks for your reply and info, I think I will need something (from memory) more than 4mm as the Jimmy Green one is.
Backstays something like 10mm. and shrouds possibly 6mm.
Regards
Mike
Strathglass
New member
Hi Mike
If you click just to the right of the 4mm line on the Jimmy Green marine web site you will find that they do four different gauges up to 10mm.
Hope you are not 6 and 10mm or you will need two gauges.
I have made all my rigging 8mm to make life easier for myself.
Cheers
Iain
If you click just to the right of the 4mm line on the Jimmy Green marine web site you will find that they do four different gauges up to 10mm.
Hope you are not 6 and 10mm or you will need two gauges.
I have made all my rigging 8mm to make life easier for myself.
Cheers
Iain